pituitrin and cobaltous-chloride

Microinjection of the cholinergic agonist carbachol into the bed nucleus of the stria terminalis (BST) has been reported to cause pressor response in unanesthetized rats, which was shown to be mediated by an acute release of vasopressin into the systemic circulation and followed by baroreflex-mediated bradycardia. In the present study, we tested the possible involvement of the hypothalamic paraventricular (PVN) and supraoptic (SON) nuclei in the pressor response evoked by carbachol microinjection into the BST of unanesthetized rats. For this, cardiovascular responses following carbachol (1 nmol/100 nL) microinjection into the BST were studied before and after PVN or SON pretreatment, either ipsilateral or contralateral in relation to BST microinjection site, with the nonselective neurotransmission blocker cobalt chloride (CoCl₂, 1 mM/100 nL). Carbachol microinjection into the BST evoked pressor response. Moreover, BST treatment with carbachol significantly increased plasma vasopressin levels, thus confirming previous evidences that carbachol microinjection into the BST evokes pressor response due to vasopressin release into the circulation. SON pretreatment with CoCl₂, either ipsilateral or contralateral in relation to BST microinjection site, inhibited the pressor response to carbachol microinjection into the BST. However, CoCl₂ microinjection into the ipsilateral or contralateral PVN did not affect carbachol-evoked pressor response. In conclusion, our results suggest that pressor response to carbachol microinjection into the BST is mediated by SON magnocellular neurons, without significant involvement of those in the PVN. The results also indicate that responses to carbachol microinjection into the BST are mediated by a neural pathway that depends on the activation of both ipsilateral and contralateral SON.

Topics: Animals; Carbachol; Cholinergic Agonists; Cobalt; Functional Laterality; Hypothalamus, Anterior; Male; Microinjections; Neural Pathways; Paraventricular Hypothalamic Nucleus; Rats; Rats, Wistar; Septal Nuclei; Vasopressins; Wakefulness

The medial prefrontal cortex (MPFC) is a structure that is also involved in cardiovascular modulation. The injection of norepinephrine (NE) into the prelimbic (PL) area of the MPFC of unanesthetized rats evokes a pressor response which is mediated by acute vasopressin release. Vasopressin is synthesized by magnocellular cells of the paraventricular (PVN) and supraoptic nucleus (SON) of the hypothalamus. In the present study, we endeavored to determine which vasopressin-synthesizing hypothalamic nucleus is involved in the pressor pathway activated after NE injection into the PL area of the MPFC. We report here that lidocaine microinjection into the SON did not change the pressor response evoked by NE injection into the PL. However, the response to NE was blocked by prior injection of lidocaine or CoCl(2) into the PVN, indicating that this area is responsible for the mediation of this pressor response. A neuroanatomic experiment in which the neuronal tracer biotinylated dextran amine (BDA) was microinjected into the MPFC showed a lack of axons or neuronal cell bodies in the PVN, indicating that there are no direct connections between the PL area of the MPFC and the PVN. The results suggest that the PVN is involved in the mediation of the pressor response to NE in the PL area and that this pathway must relay in other brain structures before reaching the PVN.

Topics: Anesthetics, Local; Animals; Antimutagenic Agents; Blood Pressure; Cobalt; Drug Interactions; Lidocaine; Male; Neural Pathways; Norepinephrine; Paraventricular Hypothalamic Nucleus; Prefrontal Cortex; Rats; Rats, Wistar; Sympathomimetics; Vasopressins; Wakefulness

The addition of cobalt chloride to the female rat blood serum resulted in a decrease of serum osmolality and in an increase of ionized calcium concentration probably due to ousting of calcium out of proteins and alteration of proteins characteristics. The osmolality of saline and activities of sodium, potassium and calcium in it did not change following addition of Co2+. The administration of vasopressin and dehydration were not followed by alteration of characteristics of serum reaction in response to addition of Co2+ in rats. More obvious effect of Co2+ was revealed with high initial serum osmolality.

Topics: Animals; Calcium; Cobalt; Dehydration; Female; Ions; Male; Osmolar Concentration; Potassium; Rats; Rats, Inbred Strains; Sodium; Vasopressins